A continuation of studies on the biosynthesis of fatty acids, cholesterol and carotenes is proposed. The emphasis in these studies will, however, be placed on the biosynthesis of fatty acids. In one area of study we will concentrate on the completion of immunotitrations of monospecific antibody with acetyl-CoA carboxylase and fatty acid synthetase of livers of animals in different nutritional or hormonal states. These studies are designed for the identification of those physiological states in which significant amounts of enzymatically inactive species of these enzymes are present. These studies will be followed with ones on the characterization of the inactive species and with the isolation and purification of the enzymes that effect an interconversion of enzymatically active and inactive species. A second study will be concerned with the identity or nonidentity of the two subunits of the fatty acid synthetase and with the linear organization of activities on these subunits. These problems are being attacked through selective proteolysis of the enzyme complex, the purification of the peptides that arise, and the preparation of monospecific antibodies to these peptides. These immunotitrations of antibody against partial enzyme activities of the native fatty acid synthetase complex. The antibodies will also be used to determine whether they bind to one or both of the half-molecular subunits of the fatty acid synthetase. Investigations on the further purification of the mRNA for the fatty acid synthetase complex will continue. When a sufficiently pure preparation is obtained we will attempt to prepare cDNA to this mRNA. If successful, we will then attempt to clone this cDNA. Studies on acetyl-CoA carboxylase will concentrate on the purification and characteristics of a protein that regulates the activity of this enzyme. Investigations on the effect of glucagon on the regulatory protein will also be carried out. Studies on the biosynthesis of cholesterol will be concerned without the preparation of monospecific antibody to HMG-CoA reductase and those on carotene formation will be concerned largely with the isolation and purification of enzymes that convert phytoene to acyclic and cyclic carotenes.